Here’s the view of the building if you’re facing west (though it now has a shiny new “Microsoft” sign at the top):

If you’re looking at the building from this view, there’s a large, glassed-in entrance near one of the the MBTA Kendall (red line) stairways. Just head in and take the elevator to the 2nd floor (the only option) and check in at the reception. They’ll guide you from there.